Soil can become contaminated by volatile organic compounds (VOC's) in a variety of ways. Leaking fuel tanks and pipelines, either above ground or underground, frequently contaminate soil with gasoline or diesel fuel. Underground tanks and pipelines can be particularly prone to leaks as they may have been in use for many years and, because they are buried in the soil, a slow leak may go undetected for some period of time. Industrial waste discharge and industrial accidents may also contribute to contamination of soil by VOC's.
Regardless of the source of contaminating VOC's concern for the purity of groundwater and the environment generally has given rise to the need for methods and systems for removing the contaminating VOC's from soil. Thermal stripping of VOC's from soil by heating the soil to some temperature below the combustion temperature of the VOC's has been utilized in a variety of systems, such as those shown in U.S. Pat. Nos. 4,738,206 and 4,782,625. These systems typically are designed to handle relatively low volumes of soil, however, and ultimately depend on relatively expensive techniques of capturing and disposing of the VOC's once they have been isolated from the soil, such as carbon filtration or afterburners. A need therefore exists for an efficient, high volume method and apparatus for removing and disposing of VOC's that contaminate soil.